1. Field of the Invention
The present invention relates to a bending tube that is formed as a cylindrical member and forms a bending portion that is provided on a distal end side in an insertion direction of an insertion portion to be inserted into a subject, and relates to a medical instrument.
2. Description of the Related Art
In recent years, medical instruments to be inserted into subjects, for example, endoscopes have been widely used in medical fields.
If an elongated insertion portion of an endoscope used in the medical fields is inserted into a body cavity as a subject, organs in the body cavity can be observed, and various treatments can be performed as needed using a treatment instrument inserted into a treatment instrument insertion channel provided to the endoscope.
Moreover, endoscopes are not limited to the medical fields, and are used in industrial fields. If an elongated insertion portion of an endoscope used in the industrial fields is inserted into an object such as a jet engine and a pipe in a factory, flaws, corrosion, and the like of a part to be examined in the object can be observed, and examination such as various treatments can be performed thereon.
Here, in a known configuration, an insertion portion of an endoscope is provided with, for example, a bending portion bendable in a plurality of directions. The bending portion improves an advancing property of the insertion portion in a curved portion in a conduit, and makes an observation direction of an observation optical system changeable. In the insertion portion, the observation optical system is provided in a distal end portion located on a distal end side in an insertion direction (hereinafter, simply referred to as distal end side) with respect to the bending portion.
Normally, a plurality of bending pieces made of metal such as stainless steel are coupled along the insertion direction of the insertion portion, whereby the bending portion provided to the insertion portion of the endoscope is configured so as to be bendable in, for example, two directions (top and bottom directions) or four directions (top, bottom, left, and right directions).
Moreover, the bending portion has a distal end in the insertion direction (hereinafter, simply referred to as distal end) fixed to a bending piece that is located on the most distal end side among the bending pieces. When any of two or four wires inserted through the insertion portion is pulled from an operation portion, the bending portion is bendable in any of the top and bottom directions or the top, bottom, left, and right directions.
Moreover, Japanese Patent Application Laid-Open Publication No. 2003-250762 discloses the following configuration. In order to achieve a reduction in diameter of an insertion portion, a plurality of bending pieces are not used to bend a bending portion, but a bending tube is used to make the bending portion bendable in two directions (top and bottom directions). The bending tube includes a plurality of slits that are formed at a predetermined interval along an insertion direction on each of an UP side and a DOWN side in a bending direction of the bending portion, that is, an UP side and a DOWN side of an endoscopic image (hereinafter, simply referred to as UP side and DOWN side), on an outer circumference of a cylindrical member made of a nickel-titanium alloy.
Note that, also in the bending tube disclosed in Japanese Patent Application Laid-Open Publication No. 2003-250762, distal ends of two wires inserted through the insertion portion are connected to a distal end of the bending tube. When any of the two wires is pulled from an operation portion, the bending portion is bendable in any of the top and bottom directions.
Incidentally, with regard to the bending tube disclosed in Japanese Patent Application Laid-Open Publication No. 2003-250762, it is known that the interval in the insertion direction of the slits (hereinafter, referred to as slit interval) formed on an outer circumference of a part to be bent is made shorter in order to obtain a predetermined bent shape.
The reason for this is as follows. Because each slit is formed in the bending tube in order to make a bending radius smaller at the time of bending, the bending radius can be smaller as the slit interval is smaller.
In particular, in order to improve a passing property of a distal end portion of the insertion portion through a curved portion in a small-diameter conduit, it is desirable that the bending portion having a predetermined length in the insertion direction be not bent from a proximal end thereof in the insertion direction (hereinafter, simply referred to as proximal end) but be capable of bending from a distal end thereof (hereinafter, referred to as distal end bending). Hence, it is preferable that the slit interval formed on an outer circumference on the distal end side of the bending tube be shorter.
Unfortunately, it is difficult to achieve the distal end bending of the bending portion, by simply making the slit interval formed on the outer circumference on the distal end side of the bending tube shorter.
Moreover, normally, because the two wires are inserted through the bending tube, the bending tube is provided with wire guides that hold the wires to thereby define positions of the wires in the bending tube.
Note that it is extremely difficult to integrally provide wire guides in the small-diameter bending tube and provide independent wire guides from the inside of the bending tube. In view of this, in a known configuration, hole portions communicated with the inside are provided between the slits on the outer circumference of the bending tube, wire guides independent of the bending tube are respectively inserted through the hole portions from the outside to the inside in a radial direction of the bending tube, and the wire guides are respectively fixed by bonding or the like to the hole portions.